A survey of the 11 most widely used search engines, reported in a July,
1999 issue of Nature, showed that the search engines are falling behind
in keeping up with the expansion of the World Wide Web (which is now estimated
to contain over 800 million pages). No single search engine, the study found, covered
more than 16% of the Web's contents. In contrast, a study in Science
in 1998 found that the best search engines covered more than 50% of all pages. A
comparison of these results is shown below:

Even when combined, the top 11 search engines cover just 42% of World Wide
Web pages. The study recommended that for exhaustive searches one use a search
engine that harnesses multiple single engines.

The search engine that is rapidly increasing in popularity is Google.
Their search engine scans each site every few days and updates its index on a
regular basis. For this reason, it gives the most current links with few dead
links. About 90% of this site's search engine referrals come from Google,
since it indexes virtually every page on this site.